Changed Box z dimension to dim/2.0

src/ffi_ZDC_HCAL.cpp

@@ -36,7 +36,7 @@ static Ref_t createDetector(Detector& lcdd, xml_h e, SensitiveDetector sens) {
 	int layer_num = 1;
 	int slice_num = 1;
 	double totWidth = Layering(x_det).totalThickness();
-	Box envelope (pixel_x/2.0, pixel_y/2.0,totWidth);
+	Box envelope (pixel_x/2.0, pixel_y/2.0,totWidth/2.0);
 	Volume envelopeVol(det_name+"_envelope",envelope,air); 
 	PlacedVolume pv;